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What does Minimally Invasive Spine Surgery (MISS) Mean?

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The term, “minimally invasive” is so vague that it really means nothing. There is no definition of what it is and the patient is left the nebulous feeling that the spine surgery will be the most minimal possible; but is this really true?

The two parts are:

The size of the incision

The nature of the procedure

Thus we will have a part 1 and part 2 to help answer this question.

Part 1

In traditional, open spine surgery, the doctor made an incision that was 5 or 6 inches long to retract muscles to the side and strip the soft tissues off the bone in order to see the spine. This provided the exposure for the surgeon to access the spine to remove a herniated intervertebral disk or address another problem. The length of the incision depended of the extent of surgery and the size of the patient – a heavier person had to have a larger incision to let enough light in to see down to the operative field.

One of the major drawbacks of open surgery is the pulling or retracting the muscles with a blade type of retractor and stripping the soft tissues. I have assisted on hundreds of these surgeries and believe me, it is not a pretty sight. Although the goal of muscle retraction is to help the surgeon see the problem area, it affects more anatomy than necessary.

The result is a greater potential for muscle and soft tissue injury, and patients may have pain after surgery that is different from the back pain felt before surgery, not to mention a lengthier recovery period.

MISS Is Not New

The concept of “minimally invasive” is hardly new. The concept is driven by the aspiration to reduce collateral soft tissue damage when performing any surgical procedure. It became really popular in the 1980s when knee arthroscopy replaced the large surgical incisions for knee surgery. The benefits were obvious, smaller incisions, less bleeding, less pain, quicker recovery, and outpatient surgery. If you have to have your gall bladder removed today, you want a laparoscopic cholecystectomy (an endoscopic procedure) because it is less invasive for sure.

The development of “minimally invasive” techniques for knee and spine surgery can be attributed to one thing, the use of the tubular retractor to retract the soft tissues when operating. That’s it. “Minimally Invasive” means using a series of tubes going from smaller to larger are used to stretch and retract the soft tissues, for the surgical exposure.

What determines the size of the tubular retractor?
Two things:

The amount of light required for visualization

The size of the instruments needed to perform the procedure

That’s it, just those two things. Technology has continued to improve the light sources and the size of the instruments. Visualization is key, whether using your eyes to look at a magnified picture through a microscope or a magnified picture from a camera projected on a screen.

What determines the size of the incision?

The size of the tube does.

Finally, we have a definition of how “minimally invasive” a procedure is. It is defined by the diameter of the tubular retractor required to access the spine condition that needs surgery. Although the skin can stretch, the incision must be slightly greater than the diameter of the tube.

There is no question that instruments with a light source on the tip of the instrument (like knee arthroscope) will be able to use the smallest tube and therefore have the smallest incision. And the smaller the tube is, the more avenues that are open to approach a painful spine condition, avenues that further eliminate soft tissue damage.

For example, a small 4 mm tube can approach the disc in the lumbar spine through a transforaminal approach without any bone removal. The transforaminal approach, which doesn’t require any bone removal is less invasive than than a procedure that requires some removal of the lamina.

So if you are wondering how “minimally invasive” a procedure is, you need to know the diameter of the tube used. There is a whole lot of difference of skill to perform surgery through a 26 mm tube than a 4mm tube! Currently, Endoscopic Spine Surgery is the most minimally invasive spine surgery there is since the tube it is performed through is the smallest.

And last but not least, remember that minimally invasive doesn’t tell you what type of procedure you are getting. A fusion can be performed through a tube these days, which I don’t consider a minimal type of surgery!

Stay tuned for part 2 of this article where I will talk about the how the nature of the procedure affects how minimally invasive a surgery can be.